Device for measuring the density of a flowing medium

ABSTRACT

The device includes a pipe section in loop form having two arms which make an angle with the horizontal, which arms each contain two pressure sensors which are located some distance apart in the direction of flow, as well as a processing unit, connected to the pressure sensors, for determining the density of the medium on the basis of the pressures or an associated parameter measured by the sensors. The pipe section in loop form is connected in parallel to the pipeline.

FIELD OF THE INVENTION

The invention relates to a device for measuring the density of a flowingmedium such as a mixture of water and particulate material, in apipeline, comprising a pipe section in loop form having two arms whichmake an angle with the horizontal, which arms each contain two pressuresensors which are located some distance apart in the direction of flow,as well as a processing unit, connected to the pressure sensors, fordetermining the density of the medium on the basis of the pressures oran associated parameter measured by the sensors.

BACKGROUND OF THE INVENTION

A device of this type is disclosed in WO-A 95/04869. With this knowndevice, the pipeline has a pipe section in loop form connected inseries, which has approximately the same capacity (cross-sectional area)as the remainder of the pipeline. With this device the full flow ofmedium is fed through the pipe section in loop form.

In order to obtain a reliable measurement of the density, variousconditions must be met. First of all the pressure sensors must be in aregion of the arms of the pipe section in loop form where the flow isreasonably undisturbed. This means that they must be located in thestraight section of the arms and, moreover, some distance away from thesubsequent bend sections. This distance increases with the diameter ofthe pipeline.

Especially in the case of pipelines having a relatively large diameter,this leads to a section in loop form of appreciable dimensions, forexample 5 to 12 meters high in the case of a vertical set-up of thearms. The cost of such a construction is appreciable.

SUMMARY OF THE INVENTION

The aim of the invention is to provide a device which does not havethese disadvantages. Said aim is achieved in that the pipe section inloop form is connected in parallel to the pipeline.

Connecting the section in loop form in parallel offers the possibilityof allowing the (main) pipeline itself to continue straight undisturbed.Only a faction of the flow of medium is diverted in order to perform adensity measurement. As a consequence thereof, the cross-sectionaldimension of the pipe section in loop form can remain restricted, which,in turn, has the consequence that the total height thereof can remainrestricted. Nevertheless, a reliable density measurement can still becarried out in such a relatively small section in loop form since theflow has already become sufficiently quiescent a shorter distance awayfrom the bend sections and has a relatively uniform character.

The connections from the pipe section in loop form to the pipeline canbe some distance apart in the direction of flow of the medium throughthe pipeline. Incidentally, said connections can also be alongside oneanother.

To promote the measurement flow, the pipe section in loop form cancontain a pump to promote the flow through the pipe section.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be explained in more detail below with reference toan illustrative embodiment shown in the FIGURE.

DETAILED DESCRIPTION OF THE INVENTION

In the FIGURE, 1 indicates a pipeline through which a medium flows inthe direction indicated by arrow 2. Said medium can be a mixture of forexample, water and sand, such as is obtained during dredging work.

The device according to the invention, which is indicated in itsentirety by 3, is connected to said pipeline 1. Said device 3 comprisesa pipe section 4 in loop form which is connected by its feed 5 anddischarge 6 to the pipeline 1. The discharge 6 is located in thedirection of flow 2 downstream of the feed 5.

By means of a pump 7, a portion of the medium is pumped from thepipeline 1 into the pipe section 4 in loop form, in accordance with thearrows indicated here.

The pipe section in loop form has two essentially vertical arms 8, 9, ineach of which sensors 10, 11 and, respectively, 12, 13 are located. Saidsensors are suitable for measuring a pressure or a unit correspondingthereto in the medium flowing through the pipe section 4 in loop form.

The diameter of the arms 8, 9 is appreciably smaller than the diameterof the pipeline 1, which means that only a portion of the medium flowsthrough the device 3.

The sensors 10-13 are positioned some distance away from the bendsections 14, 15, 16 of the pipe section 4 in loop form, so that arelatively undisturbed flow of medium prevails at the location of saidsensors. By this means a reliable measurement is also ensured.

The sensors 10-13 are connected via leads, which are not shown, to aprocessing unit, which is known per se and is not shown, for processingthe measured pressure data in the manner indicated below:

Δp _(j) =c½ρv ²+ρ_(m) gh

Δp _(II) =−c½ρv ²+ρ_(m) gh

 Δp _(j) +Δp _(II)=2ρ_(m) gh

$\rho_{m} = \frac{{\Delta \quad p_{I}} + {\Delta \quad p_{II}}}{2{gh}}$

where:

Δp_(j)=p11−p10

Δp_(II)=p12−p13

p10 to p13=pressure at the location of sensors 10 to 13

g=acceleration due to gravity

c=constant factor

v=velocity of medium

h=difference in height between sensors 11 and 10 and sensors 12 and 13

ρ=density of medium

In the FIGURE the pipeline 1 is shown in the vertical position. However,this is not necessary; the pipeline 1 can be in any position, includinghorizontal. The arms 8, 9 likewise do not have to be verticallyoriented, but must be at a certain slope with respect to the horizontal.

What is claimed is:
 1. A device for measuring the density of a flowingmedium in a pipeline, the device comprising a pipe section in loop formhaving two arms which make an angle with the horizontal, each of thearms contains two pressure sensors located some distance apart in adirection of flow, as well as a processing unit, connected to thepressure sensors, for determining the density of the medium on the basisof pressures or an associated parameter measured by the sensors, thepipe section in loop form is connected in parallel to the pipeline, andwherein the pipe section in loop form is smaller in cross-sectional areathan the pipeline.
 2. The device according to claim 1, whereinconnections from the pipe section in loop form to the pipeline are somedistance apart in the direction of flow of the medium through thepipeline.
 3. The device according to claim 1, wherein the pipe sectionin loop form contains a pump to promote the flow through the pipesection.
 4. The device according to claim 1, wherein the arms of thepipe section in loop form are essentially vertically oriented.
 5. Thedevice according to claim 1, wherein the arms are identical incross-sectional area.
 6. The device according to claim 1, wherein thetwo arms are parallel to one another and are parallel to the pipeline sothat flows of the medium through the arms and the pipeline are parallel.7. The device according to claim 6, wherein the arms are parallel to theportion of the pipeline between connections from the pipe section to thepipeline.